Thermionic indicating means responsive to light variations



' 1,021 May 31 1927 J. J. DOWLING 1,63

THERMIONIC INDICATING MEANS RESPONSIVE T0 LIGHT VARIATIONS Filed March 1926 3 Sheets-sheaf. 1

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J. J. DOWLlNG THERMIONIC INDICATING MEANS RESPONSIVE T0 LIGHT VARIATIONS Filed March 2. 1926 5 Sheets-Sheet 2 Inventor 7 1,631,021 May 31 1927' .1. J. DOWLING THERMIONIC INDICATING MEANS RESPONSIVE To LIGHT .VARIATIONS Filed March 2, 1926 s Sheets-Sheet 3 Inventor 1 J IMJ /UQO k/Zttor'mgays Patented May 31, 1927.

UNITED STATES JOHN JOSEPH BOWLING, OF RA'IHGAR, DUBLIN, IRELAND.

THEBMIONIC INDICATING MEANS BESPONSIVE T0 LIGHT VARIATIONS.-

Application filed March 2, 1926, Serial No. 91,780, and in Great Britain April 15, 1925.

This invention which relates to thermionic indicating means responsive to light variations consists of improvements in or modifications of the invention claimed in the specification of my earlier Letters Patent No. 1,561,837 dated 17th November, 1925.

As explained in the said specification persistence of electric current oscillations is relied upon to prevent any indication being given that predetermined light conditions are departed from, the said current oscillainterruption by means operated by the re-,

ceiver. An important feature of the invention furthermore consists in the employment for the purpose of interrupting the action of the beam upon the photo-electric cell, of a device which is maintained invibration by magnetic impulses due to currents derived frl'ofrin the thermionic valve system or am p 1 er.

One advantage of a vibratory device for interrupting the action of the beam controlled b the receiver as referred to, resides in the variation in amplitude which results with light variation. Thus whereas the nature of the beam interruption in cases where independently driven apparatus is used is constant, and consequently the strength of the light the sole factor influencing the receiving apparatus, the variation in light produces a variation in amplitude of vibration of the vibrating device, in the proposed -modification, which tends to secure a more rapid response of the si al relay to the changed illuminating con itions. Thus, for example, as light. wanes, there will be a diminution of-strength of the current imulses of the valve system and hence a weakening of the magnetic impulses affecting the vibrator, the vibrations of which will bereduced in amplitude and still further diminish the effect upon the photo-electric cell.

It is possible to render the vibrator self starting, as by employing a suitable condenser in circuit to secure a resonance effect,

.but means may also be employed to mechanically disturb the vibrator and produce a suflicient initial vibration which will build up rapidly to a steady amplitude dependent in part upon the strength of the light beam.

Whilst a vibrating device has been herein particularly referred to, it is to beunderstood that mterrupters of various forms may be employed so long as the same are adapted to affect the beam in the way defined.

But in order that the invention may be more readily understood it will now be further described'with the aid of the accompanying drawings whereof Figs. 1 and 2 are diagrams of two arrangements, in each of which the beam proceeds through or beyond an obturator whilst Figs. 3, 4, 5and 6 are diagrams of other arrangements in which the beam is diverted by reflecting means. Fig. 7 is a semi-diagrammatic view of an glternative form of vibratory beam reflector or use in Fig. 4 for example. Fig. 8 is a similar view of a safety relay device for use with any of the arrangements and Fig. 9 shows a modification for testing a specimen.

Referring first to Fig. 1 rays of light from a constant source 1 at a distant stationare brought to parallelism by a collimating lens 2 adjacent thereto and subsequently brought to a focus at 3 by a lens 4 at the signalling station, a further lens 5 serving to concentrate the rays upon a photo-electric cell 6 introduced into the grid circuit 7 of the first valve 8 of an audio frequency valve amplifier of one or more stages, the system shown being one that is well known and per se forms no part of the present invention. One valve, in this case the final valve 9 is employed to rectify the alternating current delivered by the amplifier. The terminals 9, 10 are for connection to any suitable form of indicating device, illustrated, as in the case of my other application referred to, as a well known type of Weston moving coil relay with the coil 11 connected to lead 12 through lead 13, and through a lead 14 to a point between battery 15 and a smaller battery 16 connected in series with a regulating reslstance 17. As long as the valve system remains excited by the reception of light impulses from the source 1 the battery 15 will so preponderate over the battery 16 that the coil 11 will take up a position such that an arm 18 bears against adead contact .19. If however by reason of fog, for example, the valve system is no longer eifective,the battery 16will cause a reverse current to flow through the coil 11 and so move the arm 18 as to cause the contact 20 in the local Circuit of a bell or other suitable signal device 21 to be completed. In accordance with the present invention a tuning fork 22 is employed to interrupt the beam of light in order to produce the requisite oscillations influencing the valve system, one limb of the said fork being located at the focus point 3 and the other limb being disposed adjacent to the poles of an electro-magnet 23, the winding whereof is included in the circuit of the battery 15.

To render the interrupter self starting an adjustable condenser24 is shownas shunting the windings of the electro-magnet 23 so as to produce a resonance effect. As a further safeguard it is preferred to employ an auxiliary relay device connected in parallel with the relay and signal means 11, 21, such auxiliary device, which might also be used in lieu of the relay and signal means in Fig. 1, being shown in Fig. 8. As there illustrated it comprises a magnet winding 11 connected across the terminals 9, 10 and a vibratory spring 25 on which rides a very light relay lever 26 of slow period so as to remain lifted when vibrations have large amplitude and thus out of engagement with an adjustable contact 27 which when engaged causes the circuit of signal 21 to be closed.

Fig. 2 illustrates an arrangement in which the electro-magnet 23, through the current oscillations, serves to produce rotation of a perforated disc 28 adapted to periodically intercept the light rays at a narrow part of the path, the said disc having a series of armatures 29 as in many well known types of motor rotors.

In Fig. 3, in lieu of a tuning fork a vibratory spring 30 is associated with the electro-magnet 23, which sprin carries a mirror 31 or other suitable re ector such that parallel rays from the distant light source after being converged by a lens 32 are reflected to-the photo-electric cell 6. The valve system is substantially the same as that of Figs. 1 and 2 except that a condenser 33 is connected across the first transformer for stability. A larger amplitude may be given to the reflected beam in some cases as exemplified in Fig. 7, by mounting the H111- ror 31 upon a support 34 of flexible material attached at one edge to a vibrator 35 and at the other edge to a stationary carrier 36 about which latter edge it is moved.

It will be obvious from this figure that the electro-magnet 23 may also be made to perform the. fimction of the electro-magnet 11 of Fig. 8 before referred to.

Fig. 4 will be readilyunderstood from what has been shown in Figs. 2 and 3, the apertures in the disc 28 of Fig. 2 being replaced by mirrors 31 equivalent to the mirror 31 of Fig. 3.

The light beam may be used to better advantage by employing a modification such as shown in Fig. 5, that is to say a duplex photo-electric cell 6, having one common electrode 37, connected in the grid circuit of the first valve or else by employing two separate cells 6" as in Fig. 6, the electrode 37 of one cell being connected to the electrode 37 of the other cell. In Fig. 5 the beam is reflected but once by a single mirror 31 whereas in Fig. 6 the rays from such a mirror 31 are received upon and reflected by mirrors 38.

In the various diagrams 6 represents an ordinary resistance in series with the cell 6, but it is permissible to substitute therefor an equivalent device possessing inductance such as a choke coil.

Daylight may be cut out from the cell 6 by means of a sun cone such as is indicated at 40 in Fig. 1 which cone is made of metal and prevents the burning glass action of the sun in the neighbourhood of the receiving apparatus. The heat from the suns rays cannot reach a good focus upon the inner Wall of the cone and a gentle heating of the latter is alone possible. The existence of the distant lamp house being necessarily in the line of sight precludes rays of the sun from entering the cone so as to be coincident with its axis and if the sun happens to rise to one side or other of the lamp house however little, the result will be to cause the cone to catch the rays without coming to a proper focus. A similar cone 40 may be fitted at the transmission end to protect the lamp house from burning glass effect.

By mounting the vibrating member and such other associated parts as may be desired in an evacuated enclosure the resonance effect may be made more pronounced as the air damping resistance due to soundemission will be thereby lessened. The device in this way may be even more sensitive, rendering less amplification necessary. This feature is exemplified in Fig. 7 where the parts 23, 31, 34', 35 and 36 are enclosed in a glass vessel 41 the magnet winding being connected to leads 42 sealed in known way tion by being placed in a strong magnetic of the natural frequency of the body the amplitude of vibration may be considerable.

"This is a known method for applying alternatlng stresses toa specilnenavltll a view to testlng the resistance to fracture by long continued bending stress alternations. By allowing-thespecimen to interrupt-a light beam in a manner analogous to the tuning fork 3 of Fig. 1 the main-difiiculty of such tests, namely the keeping of the current frequency at the resonance frequency of specimenis overcome. v I

The modification necessary for such a purpose will be understood from Fig?!) where 44 represents aspecimen to betested carried by flexible supports 45 between pole pieces 46 which producea strong and constant magnetic field. The light beam is caused to pass through ali; ;ned holes 47 in the hole pieces and the specimen 44 serves to produce the current fluctuation requisite to excite the valve system, the current oscilthe specimen is put into transverse vibration due to the alternating magnetic field set up by the current. As in the other examples warning is given when the specimen 44 breaks down and lightfiuctuations are no ou'slysubjecting the said system to electric ceiv'er system.

current oscillations persistence of which isnecessary to prevent any ind' ation being .given that predetermined lig t conditions are departed from, such means being operated by pulses de'rivedflfrom the re- 2. Means of the kind herein referred to, comprising a distant source'of light from which a beam emanates, aphoto-ele'etric cell exposed to said beam of light, means adjacent the cell for narrowing the beam of light, a-

thermionic valve-systemwith which the cell aforesaid is operatively connected, and means operated by the valve system adapted the light action.

system, a source of light and a photo-electric cell associated with the valve system'and responsive to the beamemanating from the source of light, of means for interrupting the action of the beam upon the cell adapted to be maintained invibration by magnetic impulses due tocurrents derived from the valve system. I

4, In means of thekind herein referred to,

the combination witha thermionic valve system, a sourceof light anda photo-electric cell associated with the valve system, of reflecting means adapted to periodically direct a beam of light from" the source upon the said cell, said reflecting means being dis.-

placed by electromagnetic impulses due to I currents derived from the valve system.

5. In means of the kind herein referred to, the combination with a thermionic valve sys- -,tem, a source of light and a photo-electric lations from which are conducted to the specimen 44 through the supports 46 so that cell associated with the valve system, ofa system of reflectors part of-which is stationary and part of which is movable under control of the valve system so as to periodically direct a beam of light from the source upon the said cell.

6. In means of the kind herein referred to,

the combination with a source of light, a' thermionic valve system and means operated by the latter for periodically interrupting action 01 the source oflight, of a duplexphoto-electric cell, associated with the valve system so that the latter is subjected to electric oscillations due to interruption of 7. In means of the kind hereinreferred to, a source oflight, a photo-electric cell exposed thereto, a, 'therm'ionic valve system associated with Sl1Ch cell, and a vibrating device responsive to current impulses in the valve system adapted .to interrupt the action of the light upon the cell, variation in light producing a variation in am lltude of vibration of the interrupter, su antially as described.'- I i I Signed at Dublin,'Ireland, this tenthday of February, 1926.

JOHN JOSEPH DOWLING. 

